Studies of Heart Function and Rhythm
Most of you have already undergone an electrocardiogram or ECG/EKG which detects the electrical activity of your heart and produces tracings on paper of your heart rhythm. By ‘reading’ these graphs, a cardiologist can recognize the presence of various heart rhythm abnormalities including irregularities in the rate and pattern of heartbeats, damage to the muscles of the heart and its electrical conduction system, and the effects of various drugs and procedures (e.g. insertion of a pacemaker) on the heart. Because all MACS Study participants’ involvement in this longitudinal study includes years of follow up, knowledge of heart electrical (rhythm) conduction patterns may help identify factors that could result in the development of cardiac abnormalities. Likewise, comparisons between HIV-infected and uninfected individuals may help to identify factors that cause earlier (at a younger age) onset of heart disease in HIV-infected persons. As of May 10, 2017, the Chicago MACS Study and its participants had contributed 305 ECGs to this initiative. 1,563 ECGs have been performed across the four study centers nationally.
On the day the ECG was performed, you were asked to wear a small heart monitor, known as a ZIO patch, on your chest. This device records your every heartbeat for as long as you wear it, optimally for a period of up to 14 days. The longer the monitor is worn, the more likely it is to detect infrequent, but still significant, heart rhythm irregularities. After wearing the ZIO patch, the device is mailed to iRhythm Technologies where computer programs are used to scan the device for evidence of heart rhythm irregularities that are then reviewed by a cardiologist. This allows for the diagnosis of conditions such as atrial fibrillation (an irregular rhythm of the upper chambers of your heart) and other abnormal heart rhythms. Uncontrolled heart rhythm abnormalities can cause blood clots, strokes, heart failure and other complications if not treated appropriately. Fortunately, there are excellent treatments available for these irregular heart rhythms. In fact, several MACS Study participants have received treatment for conditions detected by this heart monitor. As of May 10, 2017, the Chicago MACS Study and its participants had submitted 252 heart monitors for analysis. 1,209 monitors were submitted across the four centers nationally.
Beginning in October 2017, we will be asking you to undergo an echocardiogram or “echo”. For this painless procedure, a technician spreads a water-based gel on your chest and then presses a device (transducer) firmly against your chest which produces a harmless ultrasound beam that passes through your chest to your heart. The transducer then records the sound waves that bounce back from your heart (known as ultrasound echoes) allowing for the production of computer-generated moving images of your heart that are recorded and displayed on a monitor.
By studying these echo images of your heart, the cardiologist can learn important information about the flow and pressure of blood through the arteries of your heart; the structure, size and shape of your heart; the capacity of your heart to pump blood; the functioning of the valves controlling blood flow within and from your heart to major arteries; and the location and extent of any tissue damage to your heart. This test, combined with the ECG and ZIO patch, can provide a very detailed picture of the overall function of your heart and the nature of any abnormalities that may predict future heart-related health problems. By comparing the results of the echocardiograms in HIV-uninfected and infected men, we may be able to identify risk factors for heart disease that occur in association with HIV infection. Results and interpretation of your echocardiogram will be sent to you along with a copy of the physician’s report which you can share with your doctor. The echocardiogram, if done as a screening test outside the study, usually costs about $1,500.
Studies of Lung Function
Since April 1, 2017 (and through September 30, 2017), we have been asking you to participate in studies of lung function called spirometry and carbon monoxide diffusing capacity (DLCO for short). Spirometry is the most common lung function test. This test requires you to blow as hard as possible into a mouthpiece connected by a tube to a machine called a spirometer. The spirometer measures how much air you inhale and exhale, and how quickly you can move the air out of your lungs. The instrument generates graphs and measurements of the volume and speed of these air movements. The test is repeated after you inhale medicine that relaxes the muscles in your airways (bronchodilator). Carbon monoxide diffusing capacity indicates how well your lungs transfer inhaled oxygen into your blood. This test requires one additional tube of blood to be drawn on the same day as the PFT testing. The results of these tests are interpreted by a pulmonologist (lung doctor) in order to identify abnormalities in lung functioning that may have been caused by smoking; prior infection(s); impairments in lung airflow such as asthma, chronic bronchitis or emphysema; chronic exposure to pollutants in the air; or the impact of allergens, such as pollens. The lungs have a tremendous reserve capacity, so early changes in lung health and function may be occurring even though the person is unaware of any problem. Again, by comparing the results of lung function tests between HIV-uninfected and infected men, we may identify factors specific to HIV-infected persons that may lead to premature reductions in lung function and capacity. As with the other tests, we will provide you with the results along with a report which you may share with your doctor.
Sleep apnea is a common disorder that causes pauses (or stops) in breathing lasting anywhere from a few seconds to minutes while you are asleep. Sleep apnea can affect one’s quality of life and health because of daytime sleepiness and fatigue. Apnea can also induce changes in one’s metabolism, nervous system, and cardiovascular system. For reasons that are unclear, sleep apnea and other sleep disturbances are prevalent among HIV infected persons. This may be due to effects of the virus on the immune system or the effects of antiretroviral medications on metabolism. The MACSStudy is currently in the planning stages for conducting an overnight home sleep study to evaluate sleep quality and severity of sleep apnea in HIV-infected as compared to uninfected men. The study will also look to see if sleep apnea is linked to cardiovascular and metabolic diseases in both HIV infected and uninfected men. This study is scheduled to begin on March 1, 2018.